Exemplary embodiments pertain to the art of retrofitting elevator machines with braking functionality.
Elevator systems are useful for carrying passengers between various levels in a building. There are various types of elevator systems. Some are referred to as traction-based systems because of reliance upon traction between a drive sheave and hoisting ropes to move and position the elevator car. Elevator machines in traction-based systems include a motor and a brake. There are a variety of known brake configurations.
Supplemental brakes for conventional elevator machines are known. Some elevator codes require braking functions that are not provided by older machines. Supplemental brakes can be added to meet such code requirements. One type of supplemental brake is referred to as a rope grabber because it provides a mechanism for clamping onto the roping arrangement. A rope grabber prevents the roping arrangement from moving, which maintains a position of an elevator car within a hoistway.
Rope grabber braking has drawbacks. One drawback is that the rope grabber system needs to be positioned below the elevator machine drive sheave. This requires taking up space within the hoistway or raising the elevator machine within a machine room for providing adequate spacing for the rope grabber system. Raising elevator machines is very costly, requires adequate clearance in the machine room, and may require new ropes. Such installation is cramped, resulting in limited accessibility for future service. Additionally, some elevator applications exceed the capability of existing rope grabbing devices, or have other space limitations. Rope grabbers, by applying braking forces directly onto the ropes, increase rope wear.
Other options to meet new braking requirements include replacing the existing elevator machine with a completely new machine, which includes the necessary braking capabilities. Such action, however, can be costly and time consuming, and results in wasting otherwise serviceable elevator machinery.
There is a need to enhance braking of installed elevators while eliminating the requirements of: (1) directly applying braking forces to elevator ropes; (2) mounting an additional braking device in the hoistway; (3) raising the elevator machine to accommodate proper braking; and (3) completely replacing elevator machinery, which results in unnecessary waste. On the other hand, there is a need for elevator machinery to include both a primary braking system and a secondary emergency braking system, per safety code requirements.